Mineral oil compositions containing tincontaining dithiophosphate compounds



John P. McDermott, Springfield, N. 1., assignor to Esso' Research and Engineering Company, a corporation of Delaware No Drawing. Application September 21, 1953, Serial No. 381,512

9 Claims. (Cl. 2552-32-7) The present invention relates to a new class of tin-containing compounds and more particularly to the use of these compounds as additives for various hydrocarbon products. 7 I

I This is a continuation-in-part of Serial No. 256,597, filed November 15, 1951, and now abandoned.

In the development of.marketable hydrocarbon products such as lubricating oils, the trend has been to use more and more efficient refining methods in order to improve their stability and reduce their tendency to form carbon and deposits of solid matter or sludge. While such highly refined materials possess many advantages, their resistance to oxidation, particularly under conditions of severe service, is generally decreased and they are more prone to form soluble acid oxidation products which are corrosive. They are generally less effective than the untdStates,PatenfC treated products in protecting the metal surfaces which they contact against rusting and corrosion due to oxygen and moisture. Such lubricants also often deposit thick films of varnish on hot metal surfaces,-.such as the pistons of internal combustion engines.

In accordance with the present invention a new class of chemical compounds has been discovered, and these compounds have been found to reduce the tendency of refined lubricating oils and other hydrocarbon products to corrode metal surfaces when added in small quantities to such materials. These additives are active in reducing the corrosion of copper-lead and cadmium-silver bearings which are employed in internal combustion engines; they are likewise effective in inhibiting the oxidation of hydrocarbon products generally and especially those of petroleurn origin, and they impart other useful properties to various products.

The new class of compounds forming the subject of the present invention are tetravalent tin compounds having four organo radicals comprising at least two oil solubiliz ing hydrocarbon radicals attached directly to the tin through carbon atoms and having at least one dithiophosphate radical attached directly to the tin through a sulfur atom. The compounds are conveniently formed by reacting an organo tetravalent tin halide with a salt of a dithid phosphoric acid in such manner that halogen in the tin compound is substantially completely replaced by the organic radical. The compounds are stable and soluble in the usual hydrocarbon products such as fuels, lubricating oils and the like, are good anti-corrosive agents for organic materials that tend to corrode the usual metals, and have other useful properties.

The new class of compounds of the present invention may be more accurately defined by the following general formula:

' S ZRI (R)wSn -siy \ZR I wherein R is a hydrocarbon radical, w is 2; to 3, y is 1 to 2 and w plus y totals 4. R is also a hydrocarbon radical,

and Z is selected from the class consisting of oxygen and the following formula:

2,786,812 1 'latented" M811; 25,1

sulfur. R and R each preferably have 1 to 20 carbon atoms and may be alkyl, alkenyl, cyc'lo-alkyl, aryl, aralkyl, and alkaryl radicals. Alkyl radicals such as methyl, isopropyl, octyl, 'dodecyl, octadecyl'and other straight or branched chain radicals are preferred. Otherradicals include phenyl, naphthyl', benzyl, octylphenyl, ethylcyclohexyl, and the like. R and R should include suilicient caroon atoms to render the compound solublein hydlrocarbon products and preferably a total of at least 10 carbon atoms are contained in R and R;

The organo tetravalent tin halides used in the preparation of the compounds of the present invention may be represented by the following formula:

wherein R is a hydrocarbon radical as defined above, X is a reactive halogen such as chlorine, bromine and iodine, w is 2 to 3, y is l to 2 and w plus totals 4. Specific compounds include dibutyltindichloride, triphenyltiniodide, tri-tert.-octyltiniodide, tri-cyclohexyltinchloride, din-hexyl-tindibromide' and the like. The halide preferably has two R radicals, and the R radicals are preferably alkyl radicals. The organo tetravale'nt halides may be prepared by means well known to the art. I

The salts of dithiophosphoric acids'are represented by RZ s Diester of dithiophosphate Z in the above formulas may be either oxygen or sulfur although oxygen is generally preferred. R has the meaning defined above. Y is a cation and is preferably ametal equivalent of hydrogen. The reactive alkali .and alkaline earth metals such as sodium, potassium, calcium and the like may be used. Ammonium or amine salts may also be used. The dithiophosphates are prepared by .wellknown means. a

Specific salts of the above general types includepotassium, sodium, lithium, barium, ammonium andzthe like salts of diethyldithiophosphoric acid, isoprcpyl ethyl dithiophosphoric acid, didodecyl dithiophosphoric acid, di butyl dithiophosphoric acid, diphenylethyl dithiophosphoric acid, (di-(methylcyclohexyl) dithiophosphoricacid, di-(2-ethylhexyl)dithiophosphoric acid, dicetyldithiophosphonic acid, di-Lorol-B dithiophosphoric'acid (where Lorol-B compounds are derived from Lorol-B alco hol which is a commercial mixture of higher alcohols commonly derived from coconut oil and having from 8 to 18 carbon atoms per molecule), di(butyl mercapto) dithiophosphoric acid, and the like.

The particular compound selected will'depend largely on the concentrations used and the specific properties to be improved in various hydrocarbon products. In addition to their antioxidant properties, the dithiophosphate derivatives will sometimes be especially valuable for imparting mild extreme pressure properties to gear oils and the like. The dithioester dithiopho'sphate derivatives will generally be preferred for cutting oils where high sulfur concentrations are desired. I

Sufficient salt of the acid'is reacted with the tin halide compound to replace the halogen substantially completely. A typical reaction is represented by the following formula:

Thus from 1 to 2 mols of the desired dithiophosphate radical will be used for tin compounds having from 1 to 2 atoms of halogen although it may be desired to use excess salt in order to insure complete reaction. In carrying out the reaction, the salt may be added relatively slowly to the tin halide with care being taken to prevent excessive temperature rise as a result of the exothermic reaction which takes place. The reactants may be heated together for a period of from about 0.5 to 2 hours, depending on the types of materials present. Preferably, the reaction temperatures are maintained in a range of about 10 to 100 C. Conveniently, the reaction is carried out in the presence of an inert solvent in which the halide reaction by-products are insoluble or from which such by-products may be readily removed. Such solvents include petroleum ether, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, dioxane and the like. The heating step may be carried out under refluxing conditions when a solvent is used. The resulting metal halide will generally precipitate out of solution and may be removed by filtration, decantation or by other means. Solvent may be removed from the finished product by stripping with nitrogen or other inert gas, by distillation or by other means. A desired method for producing a relatively pure product is to filter the material, preferably before solvent is removed, through a diatomaceous filter aid such as Hy-flo."

If the products of the present invention are added to a mineral oil for inhibiting oxidation and preventing corrosion of metal parts and the like, they are preferably used in proportions of about 0.01 to 5% or by weight based on the total composition. A preferred range is from about 0.1 to 2% by Weight. Concentrations up to as high as or even higher may be used for extreme pressure lubricants, cutting oils, and the like. It is usually preferred, when marketing the additive commercially and especially when intended for use in lubricating oils, to prepare a concentrated lubricating oil solution in which the amount of additive in the composition ranges from about 20 to 50% or up to 75% by weight, depending on the solubility of the additive in the oil. The concentrate is then conveniently transported and stored in such form and may be subsequently blended with a base lubricant in the required amount before being used as a crank case oil or the like.

The invention will be more fully understood by reference to the following examples. It is pointed out, however, that the examples are given for the purpose of illustration only and are not to be construed as limiting the scope of the present invention in any Way.

EXAMPLE I.PREPARATION OF PRODUCTS Product A.Dilauryltindi-(diisopropyldithiophosphate) A mixture of 26.4 g. dilauryltindichloride (0.05 mol), 25.2 g. potassium diisopropyl dithiophosphate (0.1 mol) and 250 ml. of petroleum ether was stirred at room temperature for two hours in a S-necked 1 liter flask equipped with a thermometer and reflux condenser. The reaction mixture was then heated at reflux (50 C.) for two hours followed by filtration, whereupon 7.5 g. of ciystalline white precipitate was obtained (theoretical for KCl=7.4 g.). The filtrate was poured into an evaporating dish and placed on the steam bath to remove the solvent. A viscous, light brown liquid was obtained which analyzed 6.6% P, 14.2% S, and 12.4% Sn.

Product B.Dibutyltindi-(dimethylcyclohexyldithiophosphate) This preparation was carried out as described in connection with Product A, using 18.2 g. dibutyltindichloride (0.06 mol) and 43.2 g. potassium dimethylcyclohexyl dithiophosphate (0.12 mol). A viscous, yellow oil was obtained which analyzed 6.7% P, 13.2% S, and 8.8% Sn.

Product C.--Dibutyltindi-(dioctylphenyldithiophosphate) This reaction was conducted as described in connection with Product A, using 15.2 g. dibutyltindichloride (0.05 mol) and 54.4 g. potassium-dioctylphenyldithiophosphate (0.1 mol). A brown waxy solid was obtained which, upon analysis was found to contain 3.0% P, 5.3% S, and 4.5% Sn.

EXAMPLE II Laboratory bearing corrosion test A blend was prepared containing 0.25% by weight of the products prepared as described in Example I using as the base oil a solvent extracted, parafiinic type mineral lubricating oil of S. A. E.-20 viscosity grade. Samples of these blends and a sample of the unblended base oil were submitted to a laboratory test designed to measure the effectiveness of the additive in inhibiting the corrosiveness of a typical mineral lubricating oil towards the surfaces of copper-lead bearings. The test was carried out substantially as described in Example 12 of U. S. Patent No. 2,529,303 to McDermott. The results are reported in the table below as Bearing Corrosion Life which shows the number of hours required for the -4a Bearing Corrosion Lite (Hours to lose mg. per 25 sq. cm. of Cu- Pb bearing) Product in Base Oil (0.25 wt. percent active ingredient) The additives of the present invention may be used in various lubricating oil base stocks derived from pctroleum distillates and residuals refined by conventional means. Hydrogenated oils or white oils may be employed as well as synthetic oils prepared by polymerization of olefins, by reaction of oxides of carbon with hydrogen, or by hydrogenation of coal. The products may also be used in the synthetic polyether and polyestertype lubricants and the like as such or blended with mineral lubricants. The lubricants will usually range from about 35 to seconds (Saybolt) viscosity at 210 F.

Other agents may of course be employed in the oil compositions, such agents including dyes, pour point depressants, sludge dispersers, thickeners, viscosity index improvers, oiliness agents, and the like. In addition to being employed in lubricants, the additives of the present invention may also be used in other mineral oil products such as motor fuels, heating oils, hydraulic fluids, cutting oils, turbine oils, transformer oils, gear lubricants, greases and other products containing mineral oils as ingredients.

What is claimed is:

1. A mineral oil product having incorporated therein in the range of about 0.01 to 20% by weight of an organo tetravalent tin compound of the formula wherein Z is selected from the class consisting of oxygen and sulfur, and R and R represent hydrocarbon radicals having 1 to 20 carbon atoms.

2. A composition as in claim 1 wherein said oil product is a lubricating oil.

3. A composition as in claim 1 in which R is an alkyl radical.

4. A composition as in claim 1 wherein the R groups are alkyl radicals.

5. A composition as in claim 1 wherein the R groups are alkaryl radicals.

6. A mineral lubricating oil composition containing dissolved therein in the range of 0.1 to 2% by weight, based on the total composition, of dilauryltindi-(diisopropyldithiophosphate) 7. A mineral lubricating oil composition containing dissolved therein in the range of 0.1 to 2% by weight, based on the total composition, of dibutyltindi-(dimethylcyclohexyldithiophosphate) 8. A mineral lubricating oil composition containing dissolved therein in the range of 0.1 to 2% by weight, based'on the total composition, of dibutyltindi-(dioctylphenyldithiophosphate) 9. A concentrate consisting essentially of a hydrocarbon oil and about 20 to 50% by weight based on said concentrate of an organo-tetravalent tin compound of the formula wherein Z is selected from the class consisting of oxygen and sulfur, and R and R represent hydrocarbon radicals having 1 to 20 carbon atoms.

References Cited in the file of this patent OTHER REFERENCES Lowy et al.: Introduction to Organic Chemistry, 6th edition, page 213. 

1. A MINERAL OIL PRODUCT HAVING INCORPORATED THEREIN IN THE RANGE OF ABOUT 0.01 TO 20% BY WEIGHT OF AN ORGANOTETRAVALENT TIN COMPOUND OF THE FORMULA 